A hydraulic gantry is a well-known lifting and moving device having two or more hydraulic jack legs, one or more header beams, and devices for rigging. The hydraulic jack legs are capable of lifting very large loads, e.g., for construction, storage or transportation purposes. Hydraulic jack leg units use hydraulic cylinders, and loads are conventionally rigged to and hang from the header beam. Once the load is lifted, the load may be transported with hydraulic propel jacks or hydraulic propel wheels.
A hydraulic gantry system frequently has problems where the load must be lifted above an obstruction before it can be transported, but there is limited head room for lifting. A gantry conventionally requires a large amount of head room above the header beam for accommodating the strand jacks and strand guides above the header beam. With conventional gantries, an overhead obstruction often means days of disassembling the apparatus to pass under a load beam. Other extensive and time consuming steps may be taken to support the headroom problem for a conventional gantry system, although the conventional solution continues to involve disassembly of the load and/or special rigging.
One prior art system uses a specially made support frame to support the load, lifting bars to lift the support frame and the load, and separate suspension bars to suspend the load from the header. This design has three components to handle the load, namely a special support frame, a lifting bar, and a suspension bar. This system is both expensive to manufacture and maintain, and time consuming to use.
A gantry system with adjustable side supports is disclosed in U.S. Pat. No. 4,381,839. U.S. Pat. No. 4,718,563 discloses an overhead gantry spanning a roadway. A gantry with a harmonic lift drive is disclosed in U.S. Pat. Nos. 6,543,605, and 7,073,673 discloses a wire rope reeving support system for a gantry. U.S. Pat. No. 4,057,194 discloses a container overhead transfer and storage system.
The disadvantages of the prior art are overcome by the present invention, an improved gantry lift system is hereinafter disclosed.